Acquired drug resistance by medically relevant microorganisms poses a grave threat to human health and has enormous economic consequences. Fungal pathogens pose a particular challenge because they are more closely related to humans than bacteria and share many of the same mechanisms at the molecular level that support the growth and survival of the cells comprising their human hosts. The number of drug classes that have distinct targets in fungi is very limited and the usefulness of current antifungal drugs is compromised owing to either significant toxicity for the patient receiving them or the frequent emergence of high grade resistance. The objective of this project is to discover new chemical compounds capable of reversing fungal drug resistance, thereby illuminating the mechanisms responsible for drug resistance in disease-causing fungi and making currently available antifungal safer and more effective. To achieve this ambitious goal, a research plan designed to achieve the following specific aims will be pursued in collaboration with a designated center within the National Institutes of Health (NIH) Molecular Libraries Probe Production Center Network (MLPCN): Aim 1: Optimize and then execute a high throughput robotic screen of hundreds of thousands of individual chemicals to find compounds that can reverse the resistance of a fungal strain that was isolated from a patient receiving the very commonly used antifungal drug fluconazole Aim 2: Evaluate the compounds identified in the primary screen by measuring their potency, their spectrum of activity against various types of fungus, their selectivity for human versus fungal cells and determine the general way in which they reverse antifungal drug resistance Aim 3: Select the 10 most promising compounds and synthesize a panel of derivatives for each one to optimize their antifungal potency and specificity. This project will combine our long established expertise in studying the molecular biology of fungi using genetic and biochemical techniques with the outstanding resources of an MLPCN center and its expertise in high throughput screening technology and medicinal chemistry. In collaboration with the Broad Institute which was recently designated an MLPCN center, the essential primary screening assay has already been developed and validated. As a result, the deliverable outcome from this brief one year project is expected to be several highly useful chemical compounds with which to probe fungal biology. These probes will be invaluable to us and others for studying the mechanisms underlying fungal drug resistance. In addition to their basic research applications, their therapeutic relevance can be readily evaluated using established animal models in future work. By virtue of the way in which they will be discovered, many of these compounds are likely to act in previously unknown and unexploited ways that could prove uniquely effective in addressing the ever increasing problem of acquired drug resistance by disease-causing microorganisms that confronts our society. PUBLIC HEALTH RELEVANCE: Acquired drug resistance by disease-causing microorganisms poses an escalating threat to human health and imposes an enormous economic burden on our health care system. This project will use state of the art screening technologies to discover chemical compounds that can reverse drug-resistance in human disease- causing fungi. By virtue of the novel way in which they will be discovered, many of these compounds are likely to act in previously unknown and unexploited ways that could prove uniquely effective in tackling the serious problem of acquired antibiotic resistance that confronts our society.